General methods to retard or prevent oxidation of foods include addition of antioxidant or a substitution of air in pouches with inactive gases, for instance nitrogen or carbon dioxide, or addition of oxygen absorbing agents into pouches. As for nuts, an addition of antioxidants is not very effective. And a substitution of air with an inactive gas or addition of oxygen absorbing agents in pouches is very costly, because more precious pouch material is required to cut off an invasion of oxygen through pouch films, and these methods lose their effect after opening the pouches. It has never been previously known to treat nuts with compressed carbon dioxide gas to retard their oxidation, so this is a novel method of antioxidation and devices of this invention are also novel.